Human Embryonic Stem (HES) cells have great potential for the study of basic human development, as tools for the testing and discovery of human pharmaceuticals, and as replacement cells for transplantation therapies. Widespread dissemination of HES cells and the technical know-how necessary to culture the cells will enhance progress in HES cell research and lead to better therapies for multiple diseases, such as birth defects, diabetes, Parkinson's, leukemia, heart disease, and many other degenerative diseases. Recently, several lines of HES cells were approved for use in federally-sponsored research, including the five original HES cell lines derived by Dr. James Thomson at the University of Wisconsin (UW)-Madison. A non-profit institute, the WiCell Research Institute (WiCell), was created, in part, for the purpose of distributing UW-derived HES cells to researchers worldwide. WiCell has made one if its five lines available to researchers for the past two years. There is a need for a larger number of high quality, genetically diverse HES cell lines in order to meet the research demand, minimize the danger of changes occurring in one cell line, and to develop drugs and cell therapies for people with different genetic backgrounds. Optimization of the growth conditions for HES cells is necessary to maximize the expansion of the WiCell lines and will enhance the efforts of all researchers. The specific aims of this proposal are to: 1.) Expand the five WiCell HES cell lines to quantities sufficient to meet the demand, perform quality control tests on the five lines, and make the cell lines available to researchers along with protocols to provide information necessary to culture and expand the cell lines. 2.) Optimize the cell culture media used to culture HES cell lines to maximize their expansion, distribution and their utilization by researchers. These aims will be accomplished with: 1.) Tested HES cell expansion protocols, 2.) Standard assays for human pathogenic viruses, mycoplasma, genetic identity and karyotype analysis 3.) High throughput, HES cell-specific, cell culture media optimization protocols.